The present invention relates to contacts to bit lines in an array of programmable memory cells.
In forming contacts to source/drain bit lines in an array of programmable memory cells ordinarily contacts are made to each bit line after every 16 word lines. It has been observed experimentally that the programmability of cells in such an array varies depending on the position of the word line relative to the contacts. Transistors having word lines close to the contacts have higher programming current than those further removed from the contacts. Obviously, it is desirable to have a more uniform programming response which is independent of the position of a word line for a transistor relative to the bit line contacts.
Accordingly, it is a principal object of the invention to provide improved bit line contacts in an array of programmable memory cells.